The department has been investigating Harvard for potential civil rights violations over its affirmative action policy.

It says Harvard has failed to prove that it does not discriminate on the basis of race.

The department said the evidence in the lawsuit brought by non-profit group Students for Fair Admissions (SFFA) showed Harvard's admissions process "significantly disadvantages" academically strong Asian-Americans compared with other groups.

"No American should be denied admission to school because of their race," US Attorney General Jeff Sessions said in a statement.

The university has said in a statement it was "deeply disappointed" by the department's action and that it will defend the right of colleges to consider race as an admissions factor.

Personal traits

SFFA claims Harvard preferred white, black and Hispanic applicants, some less qualified than Asian-American students, and that it consistently ranked Asian-American applicants lowest on personal traits such as likeability.